Each message received by the wodMessage function comes with two DWORD parameters. For some messages, one of these parameters points to a structure containing additional information from the client or to an empty structure for the driver to fill with information for the client.
Waveform output device drivers use the structures listed in the following table. For detailed information on these messages, see the reference section later in this chapter.
| PCMWAVEFORMAT | A client-filled structure providing specific information about the format for PCM waveform data. |
| WAVEFORMAT | A client-filled structure providing general information about the format of waveform data. |
| WAVEHDR | A client-filled structure identifying a waveform data block. |
| WAVEOPENDESC | A client-filled structure providing information about opening a waveform device. |
| WAVEOUTCAPS | A driver-filled structure providing a client with information about the capabilities of a waveform output device. |